The Pemigewasset River is expected to flood at Woodstock this afternoon, and a flood watch is up for the three northern counties of New Hampshire, state emergency management officials said.

The National Weather Service forecast minor flooding on the Pemi from Monday afternoon through the evening.

Homeland Security and Emergency Management Director Perry Plummer said people in Woodstock should be alert and avoid driving on flooded roadways. People should also stay clear of downed power lines.

“A flood warning is issued when flooding is imminent or already happening,” Plummer said.

The flood watch for Carroll, Coos, and Grafton counties is in effect through Tuesday morning.